PHOTOVOLTAIC POWER GENERATION SYSTEM
According to an embodiment, a photovoltaic power generation system includes a photovoltaic array group and a windbreak. The photovoltaic array group includes a plurality of photovoltaic arrays, each of the photovoltaic arrays including a plurality of solar panels and a support structure which supports the solar panels. The windbreak is arranged at least partly around the photovoltaic array group and includes a plurality of windbreaker elements, each of the windbreaker having a horizontal section of an airfoil shape or a plurality of windbreaker elements each formed by combining a plurality of flat plates.
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-196134, filed Sep. 20, 2013, the entire contents of which are incorporated herein by reference.
FIELDEmbodiments described herein relate generally to a photovoltaic power generation system.
BACKGROUNDIn recent years, concerns about environmental issues are boosting the global installation of photovoltaic power generation systems that generate power using sunlight, and mega solar power plants equipped with a large-scale photovoltaic power generation system have been constructed at locations throughout the world. In the photovoltaic power generation system, a number of solar panels are arranged. These solar panels are supported and fixed by a support structure including a rack and a base. The support structure is required to have a strength capable of withstanding wind pressure and the like acting on the solar panels.
However, the installation cost of support structures makes up a large proportion of the installation cost of a photovoltaic power generation system. This proportion is larger especially in a mega solar system in which 10,000 or more solar panels are arranged. It is therefore required to reduce the installation costs of the support structures. The reduction of the installation costs of support structures can be achieved by reducing the weight of the support structures. However, it is difficult to reduce the weight of the support structures while ensuring their ability to withstand wind pressure and the like.
It is desirable to be able to reduce the installation costs of support structures in a photovoltaic power generation system.
In general, according to an embodiment, a photovoltaic power generation system includes a photovoltaic array group and a windbreak. The photovoltaic array group includes a plurality of photovoltaic arrays, each of the photovoltaic arrays including a plurality of solar panels and a support structure which supports the solar panels. The windbreak is arranged at least partly around the photovoltaic array group and includes a plurality of windbreaker elements, each of the windbreaker having a horizontal section of an airfoil shape or a plurality of windbreaker elements each formed by combining a plurality of flat plates.
Concerning a photovoltaic power generation system, JIS (Japanese Industrial Standards) C8955 defines designing a solar panel assuming four kinds of loads: a dead load caused by the mass of a photovoltaic array itself, a wind pressure load caused by wind pressure, a snow load caused by snow accumulated on the surface of a solar panel, and a seismic load caused by a seismic force. The load combination changes depending on the installation environment. The wind pressure load is a load that needs to be taken into consideration in many solar power plants, and an approximation that calculates a wind pressure load applied to a photovoltaic array from a wind velocity is applied. When applying this standard, “in case there is a plurality of racks, a wind force coefficient calculated by the formula may be applied to the peripheral ends, and ½ the value may be applied to the central portion”. However, there is no clear definition of what constitutes the central portion. For this reason, when designing a photovoltaic power generation system, it is important to appropriately estimate the region (central portion) where ½ the wind force coefficient at the peripheral ends is used so that safety can be ensured.
Embodiments will now be described with reference to the accompanying drawings. In the following embodiments, like reference numerals denote like elements, and a repetitive description thereof will be omitted.
As shown in
In general, the solar panels 112 are installed in a tilted state from the viewpoint of power generation efficiency. For example, in regions at high latitudes in the Northern Hemisphere such as Japan, the solar panels 112 are installed while tilted so that their light receiving surfaces 116 face the south. The angle made by the level surface and the light receiving surface 116 is determined in consideration of various conditions such as the latitude and environment of the installation location.
In this embodiment, a case is assumed where the solar panels 112 are arranged southward. In this case, the three photovoltaic arrays 111-1 to 111-3 are juxtaposed in a north-south direction. In each of the photovoltaic arrays 111-1 to 111-3, the solar panels 112 are arrayed in an east-west direction. In the example of
In this embodiment, each windbreaker element 121 has an airfoil-shaped horizontal section. More specifically, each windbreaker element 121 has an asymmetric airfoil-shaped horizontal section. The windbreak 120 changes the flow of air that flows from the back side of the Photovoltaic array group 110 toward the photovoltaic array group 110. The back side of the photovoltaic array group 110 here indicates the side facing the back surfaces of the solar panels 112. In this embodiment in which the solar panels 112 are arranged southward, a wind which blows from the back side of the photovoltaic array group 110 toward the photovoltaic array group 110 indicates a wind including some wind flow from the north to the south, for example, a north wind, a northeastern wind, or a northwestern wind.
For example, when a northwestern wind blows, as shown in
In this embodiment, the horizontal cross section of the windbreaker element 121 has an airfoil shape, thereby reducing the wind pressure (wind load) acting on the windbreaker element 121 itself. It is therefore possible to lower the strength of the windbreaker elements 121 and reduce the installation cost of the windbreaker elements 121.
The arrangement relationship between the photovoltaic arrays 111 and the windbreaker elements 121 will be described in detail with reference to
Note that the windbreaker elements 121 may be arranged all around the photovoltaic array group 110 or partly around the photovoltaic array group 110 in accordance with the wind state of the installation environment. For example, when installing the photovoltaic power generation system 100 in a region where a northwestern wind blows strongly but a northeastern wind does not, the windbreaker elements 121 are arranged on the north and west sides of the photovoltaic array group 110. The windbreaker elements 121 are independent, and not all the windbreaker elements 121 need always have the same dimensions and shape. In addition, the windbreaker element interval L1 need not be the same for all the windbreaker elements 121. The windbreaker element interval L1 can arbitrarily be set within a range less than the chord length C for the individual windbreaker elements 121.
The windbreak 120 may be installed not only when the photovoltaic arrays 111 have aligned ends, as shown in
The present inventors obtained wind force coefficient distributions in the photovoltaic array groups 710 and 810 of the photovoltaic power generation systems 700 and 800 by numerical analysis. Analytic models used in the numerical analysis will be described. In the numerical analysis, elements (for example, a rack and a base) other than the solar panel 112 have little effect on the wind flow and are not taken into consideration. For the photovoltaic power generation system 700, as shown in
For the photovoltaic power generation system 800, the width W of the solar panel 112 is set to 1,500 mm, the depth D is set to 2,945 mm, and the thickness T is set to 100 mm. Additionally, the height H of the solar panel 112 is set to 730 mm, and the angle φ is set to 10°. As shown in
A wind force coefficient C is defined by equation (1) below. In equation (1), a direction from the back surfaces of the solar panels 112 to the light receiving surfaces 116 is defined as positive concerning the wind force coefficient C. The wind force coefficient C represents that the larger the absolute value is, the higher the wind pressure acting on the solar panel 112 is.
P1 is the wind pressure acting on the back surface of the solar panel 112, Pu is the wind pressure acting on the light receiving surface 116 of the solar panel 112, ρ and U are the density and flow velocity of a fluid (air), respectively, and A is the area of the light receiving surface 116 or back surface of the solar panel 112.
Referring to
As described above, the tendency changes between the photovoltaic array group 710 and the photovoltaic array group 810. In the photovoltaic array group 710, a north wind swirls at the two ends and at the center of each photovoltaic array 711. In addition, a northeastern wind strikes the solar panel 112 at the east end (of the 10th column) of each photovoltaic array 711 and then flows through the photovoltaic arrays 711 while being disturbed. On the other hand, in the photovoltaic array group 810, a wind such as a northeastern wind from an oblique direction easily flows to the center region. The above-described difference in tendency probably occurs due to such a difference in the flow of air.
In this embodiment, the windbreak 120 is provided, thereby preventing a wind from directly striking the solar panels 112 at the peripheral ends of the photovoltaic array group 110 and lowering the wind pressure acting on the solar panels 112. For this reason, the central portion described in JIS C8955 described above can be more widely set. It is therefore possible to reduce the installation cost of the racks 114 and the bases 115.
As described above, in the photovoltaic power generation system according to this embodiment, the windbreaker elements are provided at least partly around the photovoltaic array group 110, thereby reducing the wind pressure acting on the solar panels. This makes it possible to ensure safety and reduce the weight of the bases and the racks. It is consequently possible to reduce the installation cost of the bases and the racks.
Note that the windbreaker element need not always have an airfoil-shaped horizontal section and can have any other shape as long as it can change the flow of air.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Claims
1. A photovoltaic power generation system comprising:
- a photovoltaic array group including a plurality of photovoltaic arrays, each of the photovoltaic arrays including a plurality of solar panels and a support structure which supports the solar panels; and
- a windbreak arranged at least partly around the photovoltaic array group and including a plurality of windbreaker elements, each of the windbreaker elements having a horizontal section of an airfoil shape or a plurality of windbreaker elements each formed by combining a plurality of flat plates.
2. The system according to claim 1, wherein each of the windbreaker elements has a horizontal section of an as airfoil shape.
3. The system according to claim 1, wherein an interval of installation of the windbreaker elements is not more than a chord length of the airfoil shape.
4. The system according to claim 2, wherein an interval of installation of the windbreaker elements is not more than a chord length of the airfoil shape.
Type: Application
Filed: Sep 18, 2014
Publication Date: Mar 26, 2015
Inventors: Tomohiko JIMBO (Fujisawa), Biswas DEBASISH (Shiki), Kei MATSUOKA (Kawasaki), Yoshiaki HASEGAWA (Tokyo)
Application Number: 14/489,621
International Classification: H02S 20/23 (20060101);